Embodiments herein include medical systems, devices, and methods for assessing the health status of a patient. In an embodiment, a method includes evaluating the presence of volatile organic compounds in a breath or gas sample of the patient with a plurality of graphene sensors to generate volatile organic compound data, wherein the plurality of graphene sensors include sensors that are specific for different volatile organic compounds. The method can further include collecting data regarding the patient's sympathetic nervous activity. The method can further include combining the volatile organic compound data with the collected data regarding the patient's sympathetic nervous activity to form a combined data set. The method can further include matching the combined data set against one or more data patterns to find the best match, the best match indicating the health status of the patient. Other embodiments are also included herein.